Apparatus for detecting leaks in a fluid delivery line

ABSTRACT

An apparatus for detecting leakage in excess of a preselected rate from a fluid delivery line through which fluid is intermittently delivered under pressure, the apparatus including a main valve which controls flow of fluid to the delivery line and having a pressure responsive operator, and a leak detecting pilot valve for controlling the application of fluid pressure to the pressure responsive operator of the main valve.

[451 Sept. 19, 1972 ksiek Pillote 8: Muir ABSTRACT S m e :g u u UnitedStates Patent Deters [5 APPARATUS FOR DETECTING LEAKS Primary Klin IN AFLUID DELIVERY LINE y- Morsbech,

[73] Assignee:

An apparatus for detecting leakage in excess of a preselected rate froma fluid delivery which fluid is intermittent the apparatus including amain valve which controls flow of fluid to the delivery line and havinga pressure responsive operator, and a leak detecting pilot valve forcontrolling the applicatio pressure responsive operator mu 1mm m mm m t."u" .l nu m mu" n 7 m 8 9 "mm M 1 "n" D 0 m In 9 s "n" V. t n a l "uh IM 4 nut l .r mm

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PAIENIED SEP 19 I972 SHEET 3 BF 3 m w, Ema m W y/Q APPARATUS FORDETECTING LEAKS IN A FLUID DELIVERY LINE BACKGROUND OF THE INVENTION Thepresent invention relates to apparatus for detecting leaks in a fluiddelivery line through which fluid is intermittently delivered underpressure and particularly relates to improvements in leak detectorapparatus of the type disclosed in the US. Fat. to Elmer M. Deters No.3,183,723 issued May 18, 1965. As disclosed in that patent, a leakdetecting valve apparatus is disposed in the fluid delivery line betweenan intermittently operated pump and a remote valved outlet, and the leakdetector valve apparatus is arranged to initially pass a restricted flowof fluid into the delivery line to rapidly pressurize the line to anintermediate pressure range, and to thereafter restrict the flow offluid into the delivery line to a rate equal to the maximum permissibleleakage rate from the line so that the pressure in the delivery linewill build up above the intermediate range only if there is nosignificant leakage from the line. If the pressure in the delivery linebuilds up above the intermediate range, then the valve is moved to itsopen position to allow substantially unrestricted flow through the line.

ln the leak detector apparatus of the above patent, the leak detectorvalve directly controls the flow of fluid to the delivery line and theentire delivery flow must pass through the leak detector valve. In orderto adapt the prior leak detector valves for handling larger flows, itwas necessary to correspondingly increase the size of the leak detectorvalve. The leak detector valve must, however, very accurately meter theflow of fluid into the delivery line at a rate corresponding to themaximum permissible leakage rate, and the leak detector apparatus mustsense and respond to relatively small changes in pressure during itsoperation. As the size of the leak detector valve is increased, theproblems of maintaining accurately metered flow are also increased.Moreover, problems are also encountered due to pressure surges in thedelivery line which may occur due to operation of the pump or the valve.

It is the object of the present invention to overcome the disadvantagesof the prior leak detecting apparatus by providing an apparatus in whicha main pressure responsive valve is used to control flow through thedelivery line and the leak detector valve operates as a pilot to controlapplication of pressure to the main valve.

Accordingly, the present invention provides a leak detecting apparatusincluding a main valve having an inlet and an outlet for passing fluidtherethrough to the delivery line, a main valve member controlling flowthrough the main valve and connected to a pressure responsive memberhaving one side exposed to pressure in a pressure chamber. Fluid fromthe main valve inlet is supplied through a control passage to thepressure chamber and a leak detector pilot valve has its inlet connectedto the pressure chamber and its outlet connected to the outlet of themain valve for controlling the pressure on the pressure responsivemember. The leak detector valve is operated when the pressure at themain valve outlet reaches a preselected intermediate range to restrictthe flow of fluid into the delivery line to a rate equal to the maximumpermissible leakage rate, and the leak detector pilot valve operates toopen and thereby allow the main valve to open only if there is nosubstantial leakage from the delivery line. The main valve isadvantageously constructed and arranged to inhibit leakage past the mainvalve due to pressure surges in the line.

A preferred embodiment of the invention is illustrated in theaccompanying drawing wherein:

H0. 1 is a diagrammatic view of a pumping system having a leak detectingapparatus of the present invention embodied therein;

FIGS. 2, 3 and 4 are sectional views through the leak detectingapparatus illustrating the same in different positions;

FIG. 5 is a fragmentary sectional view through the leak detector valveshowing the parts on an enlarged scale;

FIG. 6 is an end view of the leak detecting valve shown in FIG. 5; and

FIG. 7 is a graph illustrating the relationship between the flow openingof the leak detector, expressed in terms of gallons per minute, and thepressure in the delivery line.

The leak detecting apparatus of the present invention is generallyadapted for use in detecting leaks from a delivery line through whichfluid is intermittently delivered under pressure and is herein shown anddescribed in conjunction with a pumping system such as a gasolinedispensing system. As diagrammatically shown in FIG. 1, the pumpingsystem includes a pump 10 for pumping liquid from a storage reservoir ortank T through a pump outlet line 11 to a delivery line 12 that extendsto a remote outlet indicated at 13. A valve 14 is provided at the remoteoutlet and arranged to be closed when the pump is stopped. Provision ispreferably made for preventing drainage of fluid from the delivery line12 when the pump is stopped and, for this purpose, a check valvediagrammatically shown at 15 is provided adjacent the inlet end of thedelivery line 12. ln the pumping system, the pump 10 is intermittentlyoperated to deliver fluid under pressure to the line 12 and is hereinshown driven as by an electric motor 16. As diagrammatically shown inH6. l, operation of the motor is effected under the control of a switch17 conveniently located adjacent the outlet valve 14, which switch isconnected through a motor control unit 18 and conductors 19 to the motor16 to start and stop the same. The leak detector apparatus 21 is locatedadjacent the inlet end of the delivery line and is operable to detectleakage from the delivery line downstream of the leak detectorapparatus.

The leak detector apparatus is best shown in FIGS. 2-4 and includes amain valve 21a for controlling flow through the delivery line and a leakdetector pilot valve 21b which meters fluid into the delivery line andalso controls the application of fluid pressure to the pressureresponsive operator for the main valve. The main valve 21a includes avalve casing 23 having an inlet chamber 24 adapted for connection to thepump outlet line 11 and an outlet chamber 25 adapted for connection tothe delivery line 12, with a valve seat 26 intermediate the inlet andoutlet chambers. A main valve member 27 cooperates with the seat 26 tocontrolflow through the main valve and the main valve member is mountedby a stem 28 which is slidably supported in a guide 29 for movement intoand out of position closing the valve seat. A pressure responsiveoperator conveniently in the form of a diaphragm 31 is connected to thestem 28 and diaphragm stabilizing plates 32 are preferably provided atopposite sides of the central portion of the diaphragm to confineflexing of the diaphragm to the outer annular portion of the same. Theouter periphery of the diaphragm 31 is clamped to a flange 35 on themain valve casing and the underside of the diaphragm 31 is exposed tothe fluid pressure in the outlet chamber 25. However, for reasonspointed out hereinafter, the stem guide 29 and main valve casing arearranged to form a substantially closed chamber 36 at the underside ofthe diaphragm, which chamber has restricted communication throughpassage 38 with the outlet chamber. Passage 38 restricts flow of fluidbetween the chamber 36 and the outlet chamber and provides a dash pot atthe underside of the diaphragm for inhibiting rapid movement of thediaphragm and valve member in response to short duration pressure surgeson the valve member or diaphragm. A cap 39 overlies the upper side ofthe diaphragm 31 to define a pressure chamber 41 and is attached to thevalve casing by fasteners 40 to clamp the periphery of the diaphragm tothe main valve casing. Fluid under pressure from the pump is supplied tothe pressure chamber 41 through a control passage 28a advantageouslyformed in the valve stem. Passage 280 extends completely through thelength of the stem and communicates the main inlet chamber 24 with thepressure chamber 41. As will be seen from the drawings, the main valvemember is movable from its closed position shown in FIGS. 2 and 3, inthe direction of fluid flow through the main valve, that is in adirection away from the inlet chamber 24 to its opened position shown atFIG. 4. The effective area of the diaphragm, that is the area inwardlyof the flange 35 on the valve casing, is made substantially larger thanthe cross-sectional area of the valve seat 26 so that, when the valve isclosed as shown in FIGS. 2 and 3, pressure from the inlet chamber 24applied through passage 28a to the pressure chamber 41 will exert aclosing force on the diaphragm and valve member that is greater than theforce exerted on the valve member by the pressure at the inlet. In orderto assure closing of the valve member when the pressures at oppositesides of the diaphragm are substantially equalized, a light compressionspring 43 capable of exerting a few pounds force is provided andarranged to engage the upper end of the valve member to yieldably biasthe valve member toward its closed position.

The main valve 27 normally moves to its closed position when the pump isshut down and, when the pump is thereafter started, the fluid underpressure from the pump is applied through the inlet chamber 24 to theunderside of the valve member 27 and is simultaneously applied throughpassage 28a to the pressure chamber 41 at the diaphragm 31 to normallyhold the main valve member in its closed position. The leak detectorpilot valve 21b is arranged to pass a metered flow of liquid into thedelivery line after the pump is started and the leak detector pilotvalve controls the pressure in the main pressure chamber 41 to allowopening of the main valve in the absence of a leak. The pressure in thedelivery line can drop to a relatively low value due to thermalcontraction and the delivery line can even be substantially drained ofliquid in the event of a leakage through check valve 15 back to thetank, or opening of the outlet valve 14 after the pump is stopped. Theleak detector apparatus is accordingly advantageously arranged so that,when the pump is started, fluid is initially supplied to the deliveryline at a relatively rapid rate to fill the line and bring the line upto an intermediate leak detecting pressure which is above atmosphericpressure and below pump delivery pressure when the outlet valve isclosed. The leak detector apparatus thereafter meters fluid to thedelivery line at a controlled rate corresponding to the maximumpermissible leakage rate from the delivery line. If the leakage from thedelivery line is less than the metered rate delivered by the leakdetecting apparatus to the line, the pressure in the line will build upabove the intermediate pressure, for example 10 psi. and the leakdetector pilot valve is arranged to respond to the increase in pressureabove the intermediate pressure to discharge fluid from the pressurechamber at a rate greater than the rate of flow of fluid into thepressure chamber through passage 280. This allows the main valve to openand pass full pump flow to the delivery line. On the other hand, if theleakage from the delivery line is in excess of the metered leakage ratepassed by the leak detecting apparatus, then the pressure in thedelivery line will not build up above the intermediate pressure range.The leak detector apparatus is arranged so as to thereafter operate,when the outlet valve 14 is opened, to pass fluid at a reduced rate tothe delivery line so as to signal the operator that a leak does exist onthe line. This rate, herein sometimes referred to as a signal rate, isselected so as to be substantially less than full pump delivery rates.

The leak detector pilot valve 21b is similar to the leak detector valvedisclosed in the aforementioned U.S. Pat. No. 3,183,723 and such leakdetectors can be adapted for use as leak detector pilot valves in theleak detecting apparatus of the present invention. in the embodimentshown, the leak detector pilot valve includes a pilot valve casing 51having a pilot inlet 52 communicating through an open passage 53 withthe main pressure chamber 41, and an outlet 54 communicates throughpassages 55 and 56 with the main outlet chamber 15. As shown, passage 55is conveniently formed in a casting integral with the pilot valve casing51 and passage 56 is formed in the main valve casing 21a, the peripheralportion of the diaphragm 3S operating to form a seal at the interfacebetween the passages 55 and 56. The pilot valve includes a pilot valveseat 57 intermediate the pilot inlet and pilot outlet and, in the formshown, the seat 57 is mounted as by threaded engagement on an annularportion 580 of a cage-like member 58. The annular portion 58a is sealedto the pilot housing by an O-ring 59 intermediate the pilot inlet 52 andoutlet 54 and the cage has openings 58b to pass fluid from the pilotinlet 52 to the valve seat 57. The cage is attached, as by threadedengagement with an end portion 61a of a diaphragm housing 61, and thediaphragm housing has an enlarged externally threaded portion 61b thatis removably mounted in an opening in the pilot valve casing to allowremoval of the cage 58 and seat 57 from the pilot valve casing.

The leak detector pilot valve 21b includes a valve mechanism which isoperative to initially supply fluid to the delivery line at a rate inexcess of the leakage rate, to rapidly fill the line, and which leakdetector valve mechanism is thereafter operative, when the pressure inthe delivery line reaches a preselected intermediate pressure such asp.s.i., to restrict or meter the flow of fluid into the delivery line ata rate equal to the maximum permissible leakage rate, and to thereafteropen the leak detector pilot valve if the pressure in the delivery linerises above the intermediate range, indicative of the absence of asignificant leak from the line. In the embodiment shown, these severalvalving functions are performed by a dual valve mechanism best shown inFIGS. 5 and 6 and including a pilot valve member 65 which is adapted tospan the seat 57 and which has means such as a packing ring 68 on itsperiphery to form a sliding seal with the seat 57. The packing 68 isarranged to seal the interface between the pilot valve member 65 and theseat 57, when the pilot valve member is in a position spanning the seat.However, a bypass valve is formed in the pilot valve member 65 andincludes a valve bore 65a that extends axially through the valve memberand a lateral passage 65b that communicates the bore 65a with the outerperiphery of the valve member at the inlet side of the packing 68 sothat, when the pilot valve member is in its closed position shown inFIG. 2, fluid from the pilot inlet 52 can pass through the openings 58bin the cage 58 and through lateral passage 65b and bore 650 to the pilotoutlet. Bore 65b is dimensioned to pass fluid at a preselected ratesufficient to effect rapid filling of the delivery line, butsubstantially less than full pump flow and has a flow area which issubstantially smaller than the flow area of passage 280 that suppliesfluid from the main inlet chamber 24 to the pressure chamber 41 so thatthe pressure in chamber 41 is not reduced significantly below inletpressure during flow through the bypass passage 65b.

The pilot valve member has a pressure responsive operator which respondsto the pressure in the main outlet chamber 25 and hence to the pressurein the delivery line. As shown, the pilot valve member is connected by astem 71 to a pressure responsive member herein shown in the form of adiaphragm 72. The stem is attached to the diaphragm by diaphragmreinforcing members 73 and 73a which overlie opposite sides of thecentral portion of the diaphragm 72, and the periphery of the diaphragm72 is attached to a flange 61c on a cup-shaped head 61d on the housing61. The diaphragm and head 61d define a pressure motive chamber 74 atone side of the diaphragm and the other side of the diaphragm is ventedto atmosphere. As shown, the diaphragm is clamped to the flange 71 by avented cap 77 and fasteners 78. A sealing gland 75 is provided on thediaphragm housing to slidably engage the stem 71 and form a seal betweenthe housing and stem. Fluid under pressure from the delivery line isapplied to the chamber 74 for operating the pilot valve and in the formshown, the stem 71 is provided with an axial passage 71a thatcommunicates at one end through lateral opening 71b with the pilotpressure chamber 74 and which communicates at its other end through apassage 650 in the pilot valve member 65, with the pilot outlet 54. Aspreviously described, the pilot outlet 54 communicates through passages55 and 56 with the main outlet chamber 25 and delivery line l2.

The pilot valve member 65 is yieldably urged to its closed position by aspring 81 interposed between the valve member and the diaphragm housing61, and the diaphragm 72 is made substantially larger than the effectivecross-sectional area of the pilot valve member 65 and such as to causemovement of the pilot valve member from its fully closed position shownin FIG. 2, to an intermediate position shown in FIG. 3 when the pressurein the chamber 74 reaches a preselected intermediate pressure betweenatmospheric pressure and a full pump discharge pressure. A valve member82 (FIG. 5) herein shown in the form of a small spool is provided forrestricting the flow of fluid through the bypass passage 65b and bore65a when the pilot valve member is moved to its intermediate position.As best shown in FIG. 5, the bypass valve member 82 is connected by astem 83 to a support structure 84 conveniently formed integrally withthe valve seat 57. The valve member 82 remains stationary duringmovement of the pilot valve 65 and, when the latter reaches itsintermediate position shown in FIG. 3, the spool extends across theinner end of the lateral passage 65b. The spool is made slightly smallerthan the valve bore 65a to provide a restricted flow passagetherearound, of the order of a few thousandths of an inch, andsufficient to pass only a restricted flow equal to the maximumpermissible leakage rate. Thus, when the pilot valve member is in itsintermediate position shown in FIG. 3, fluid from the pilot inlet ispassed at a restricted rate equal to the maximum permissible leakagerate, for example of the order of a few hundredths of a gallon perminute from the pilot inlet to the pilot outlet for flow into thedelivery line. If the pressure in the delivery line builds up above theintermediate pressure at which the valve member moves to itsintermediate position, then this pressure is applied to diaphragm 72 andoperates to move the pilot valve member to its open position shown inFIG. 4. When the pilot valve is in its open position, it provides a flowpassage between the pilot inlet and the pilot outlet which issubstantially larger than flow passage 28a so that the pressure chamber41 is vented to the main outlet chamber to thereby substantiallyequalize pressures on opposite sides of the main pressure responsivemember 31. The main valve member canthen move to its open position toallow full pump flow to the delivery line. As will be seen, the pumpinlet pressure is applied to the underside of the main valve member 27and, when the pressures on opposite sides of the diaphragm 31 areequalized, the main valve member can move to its open position with onlya small difference in pressure between the main inlet and outletchambers 24 and 25. On the other hand, if the pressure in the deliveryline does not build up above the intermediate pressure range in responseto passage of fluid at the leakage rate into the delivery line, or ifthe outlet valve 14 is opened before the leak detector pilot valve movesto its open position, then the leak detector pilot valve will move backto its initial position shown in H0. 2. ln this position, the bypassvalve 82 uncovers the bypass passage 65b and allows fluid at acontrolled rate to pass into the delivery line.

if the delivery line is full when the pump is started, only a relativelysmall quantity of fluid for example, of the order of 1 pint, must besupplied to the delivery line in order to bring it up to theintermediate leak sensing range. Any leakage past the main valve memberwhen it is closed, or any flow which may occur past the main valvemember due to pressure surges in the line, could build up the pressurein the delivery line above the intermediate leak sensing range and thusbypass operation of the leak detector pilot valve. The dash pot effectproduced by the restricted passage 38 between chamber 36 and the outletchamber 25 inhibits rapid movement of the main valve member andmaterially assists in avoiding spurious opening of the main valve memberdue to pressure surges which may be caused by starting of the pump, oropening of the delivery valve.

The main valve member 27 and valve seat 26 are constructed and arrangedto provide a face type seal therebetween and for this purpose, the valveseat 26 has an annular valve face 260 that cooperates with a resilientvalve face 27a on the valve member. In addition, valve seat 26 isadvantageously formed with an axial valve face 26b and the valve member27 is formed with a lip 27b that cooperates with the axial sealingsurface 26b to form a sliding seal therebetween during initial movementof the valve member relative to the valve seat. The lip 27b thusinhibits leakage past the main valve member in the event the main valvemember is shifted slightly relative to the seat due to a pressure surge.In addition, it forms a second sealing surface to aid in preventingleakage at this point.

OPERATION In describing an operating cycle of the apparatus, it isassumed that the pump is stopped, the shutoff valve I4 is closed, andthat the pressure in the line 12 has reduced to substantiallyatmospheric pressure either due to thermal contraction in the deliveryline or leakage at the check valve 15 or due to opening of the outletvalve 14 after the pump stopped. When the pump is thereafter started inresponse to closing of the switch 17, the pump will rapidly build up thepressure in the inlet chamber 24 of the leak detecting apparatus. Thispressure is applied to the underside of the valve member 27 and is alsoapplied through passage 28a to the pressure chamber 41. Since thediaphragm 31 has an area substantially greater than the area on thevalve member 27 that is exposed to inlet pressure, the pressure on thediaphragm normally tends to hold the valve closed. The leak detectorapparatus controls flow to the delivery line when the pump is started ina manner generally depicted by the solid line curve in FIG. 7. Assumingthe pressure in the delivery line is initially below the intermediateleak sensing range, the leak detector pilot valve will initially be inthe position shown in FIG. 2 opening the bypass passage 65b and allowingfluid to flow into the outlet chamber 25 and delivery line 12 at asignal rate indicated at A in the graph of FIG. 7 to rapidly fill thedelivery line and build up the pressure in the line to the intermediatepressure range. As the pressure in the line builds up to theintermediate pressure range, it operates on the pilot diaphragm 72 tomove the pilot valve member 65 to its intermediate position shown inFIG. 3. In this position, flow through the bypass passage 65b isrestricted by the valve member 82 to a rate equal to the maximumpermissible leakage rate indicated at B in the graph of FIG. 7. Fluid atthe leakage rate continues to flow into the delivery line through theleak detector pilot valve and, in the absence of a significant leak fromthe line, the pressure will build up above the intermediate pressurerange. As previously described, the pilot diaphragm 72 is proportionedso that, when the pressure in the aforementioned intermediate pressurerange is applied to the diaphragm. it is sufficient to overcome theclosing pressure of spring 81 and the pressure unbalance on the pilotvalve member due to the differential between inlet and delivery linepressure acting on opposite sides of the pilot valve. When the pilotvalve reaches its open position, the fluid pressures on opposite sidesof the pilot valve member are equalized so that the pilot valve willrapidly move to its open position and then remain in its open positionuntil the pressure in the delivery line drops to a pressuresubstantially below the intermediate pressure range.

As the pilot valve moves to its open position, it moves past a positionsuch as indicated at C in FIG. 7 in which flow from the main pressurechamber 41 through the pilot valve exceeds flow into the chamber 4]through passage 28a so that pressure in the chamber 41 is reduced andthe main valve member can then move to its open position due to theinlet pressure acting on the underside of the main valve member 27. Ifthere is a leak from the delivery line in excess of the aforementionedleakage rate, or if the outlet valve 14 is opened before the pilot valveis opened, then the pressure in the delivery line will not build up tothe intermediate pressure range. Accordingly, if the main valve isopened under these conditions, only fluid which passes through passage28a, chamber 41 and bypass passage b, can flow into the delivery line.As previously described, bypass passage 65b limits the flow of fluid toa signal rate such as indicated at A in FIG. 7, which signal rate issubstantially below full pump discharge and thus signals the operatorthat there is a leak from the line.

When the pump is shut off, the pressure in the delivery line can againdecrease due to thermal contraction in the line or due to leakage fromthe line or past the check valve 15. However, as previously described,the pressure unbalance on the pilot valve member 65 is equalized whenthe pilot valve is in its open position so that the pilot valve does notclose until the pressure drops to a pressure substantially below theintermediate pressure at which the pilot valve opens. The dashed curvein FIG. 7 generally illustrates the relationship between the flowopening through the leak detector apparatus and the pressure in thedelivery line, when the pressure in the delivery line decreases afterthe pump is shut off.

While a preferred embodiment of the present invention has herein beenillustrated and described, it has been done by way of illustration andthe invention should not be limited except as required by the scope ofthe appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An apparatus for detecting leakage in excess of a preselected leakagerate from a fluid delivery line through which fluid is intermittentlydelivered under pressure and wherein the pressure in the line can varyover a wide range between a low pressure and a relatively higherdelivery pressure, said apparatus comprising a casing having a maininlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat, and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, a main pressure responsive member having one sideexposed to pressure in the main pressure chamber and the other sideexposed to pressure in the main outlet chamber, means connecting saidmain pressure responsive member to said main valve member for movingsaid main valve member to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main pressurechamber with said main inlet chamber and dimensioned to pass fluid fromthe main inlet chamber to the main pressure chamber at a rate in excessof said preselected leakage rate, a leak detector pilot valve includinga pilot valve casing having a pilot inlet communicating with said mainpressure chamber and a pilot outlet communicating with said main outletchamber, pressure responsive pilot valve means for controlling flowbetween said pilot inlet and pilot outlet and operative to provide arestricted flow passage between said pilot inlet and said pilot outletto pass fluid at said preselected leakage rate when the pressure in saidmain outlet chamber reaches a preselected intermediate range betweensaid low pressure and said delivery pressure, said pressure responsivepilot valve means being operative when the pressure in said main outletchamber rises above said intermediate range to open and provide a flowpassage therethrough which is relatively unrestricted as compared tosaid control passage means whereby to substantially equalize thepressure in said main pressure chamber with the pressure in said mainoutlet chamber and allow said main valve member to open.

2. in an apparatus for detecting leakage in excess of a preselectedleakage rate from a fluid delivery line through which fluid isintermittently delivered under pressure and wherein the pressure in theline can vary over a wide range between a low pressure and a relativelyhigher delivery pressure, said apparatus comprising, a casing having amain inlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, and a main pressure responsive member having oneside exposed to pressure in said main pressure chamber and the otherside exposed to pressure in said main outlet chamber, means connectingsaid main pressure responsive member to said main valve member formoving the latter to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main outletchamber with said main pressure chamber to apply fluid pressure to saidmain pressure responsive member for holding said main valve member inits closed position, pressure responsive control means operative whenthe main valve member is in its closed position and the pressure in themain outlet chamber is below a preselected intermediate pressure rangefor passing fluid at a preselected signal rate from the main inlet tothe main outlet to allow the pressure in said main outlet chamber torapidly build up to said preselected intermediate pressure range, saidpressure responsive control means including means operative when thepressure in said main outlet chamber reaches said preselectedintermediate pressure range to restrict flow from said main inlet tosaid main outlet to said preselected leakage rate, said pressureresponsive control means including means operative when the pressure inthe main outlet chamber rises above said intermediate pressure range topass fluid from said main pressure chamber to said main outlet chamberat a rate greater than the rate of flow of fluid through said controlpassage means into said main pressure chamber to thereby substantiallyequalize pressures on opposite sides of said pressure responsive memberand allow said main valve member to open.

3. In an apparatus for detecting leakage in excess of a preselectedleakage rate from a fluid delivery line through which fluid isintermittently delivered under pressure and wherein the pressure in theline can vary over a wide range between a low pressure and a relativelyhigher delivery pressure, said apparatus comprising, a casing having amain inlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, and a main pressure responsive member having oneside exposed to pressure in said main pressure chamber and the otherside exposed to pressure in said main outlet chamber, means connectingsaid main pressure responsive member to said main valve member formoving the latter to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main outletchamber with said main pressure chamber and dimensioned to pass fluid tothe main pressure chamber at a rate in excess of a preselected signalrate, a leak detector pilot valve including a pilot valve casing havinga pilot inlet communicating with said main pressure chamber and a pilotoutlet communicating with said main outlet chamber, pressure operatedpilot valve means controlling flow between said pilot inlet and saidpilot outlet operative when the pressure in said main outlet chamber isbelow a preselected intermediate pressure range to pass fluid at saidpreselected signal rate from said main pressure chamber to said mainoutlet chamber, said pressure operated pilot valve means being operativewhen the pressure in said main outlet chamber reaches said intermediatepressure range to restrict flow between the pilot inlet and the pilotoutlet to said preselected leakage rate, said pressure operated pilotvalve means being operative when the pressure in said main outletchamber rises above said preselected intermediate pressure range to openand pass fluid from the main pressure chamber at a rate greater than therate of fluid flow through said control passage to thereby allow saidmain valve member to open.

4. An apparatus according to claim 3 including means defining a secondchamber at said other side of the pressure responsive member, nd meansproviding restricted communication between said second chamber and saidmain outlet chamber to inhibit rapid movement of said main pressureresponsive member and main valve member.

5. An apparatus according to claim 3 wherein said main valve member hasmeans cooperating with said main valve seat to provide a sliding sealtherebetween during initial movement of the main valve member relativeto the main valve seat.

6. In an apparatus for detecting leakage in excess of a preselectedleakage rate from a fluid delivery line through which fluid isintermittently delivered under pressure and wherein the pressure in theline can vary over a wide range between a low pressure and a relativelyhigher delivery pressure, said apparatus comprising, a casing having amain inlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, and a main pressure responsive member having oneside exposed to pressure in said main pressure chamber and the otherside exposed to pressure in said main outlet chamber, means connectingsaid main pressure responsive member to said main valve member formoving the latter to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main outletchamber with said main pressure chamber and dimensioned to pass fluid tothe main pressure chamber at a rate in excess of said preselectedleakage rate, a leak detector pilot valve including a pilot valve casinghaving a pilot inlet communicating with said main pressure chamber and apilot outlet communicating with said main outlet chamber, pilot valvemeans controlling flow from said pilot inlet to said pilot outlet, meansresponsive to the pressure in said main outlet chamber for positioningsaid pilot valve means in an initial position when the pressure in saidmain outlet passage is below a preselected intermediate pressure rangebetween said low pressure and said delivery pressure, said pressureresponsive means being operative to move said valve means to anintermediate position when the pressure in said main outlet passage isin said intermediate range and to an open position when the pressure inthe main outlet passage is above said intermediate range, said pilotvalve means being operative in said initial position to define aninitial flow passage between said pilot inlet and pilot outlet that issmaller than control passage means to pass fluid at a rate in excess ofsaid preselected leakage rate to said main outlet chamber to rapidlyfill the delivery line, said pilot valve means including means operativewhen the pilot valve means is in said intermediate position to define anintermediate flow passage between said pilot inlet and pilot outletwhich is smaller than said initial flow passage to pass fluid at saidpreselected leakage rate to said main outlet chamber to increase thepressure in said main outlet chamber if the leakage from the deliveryline is less than said preselected leakage rate,

said pilot valve means including means operative in said open positionto define a flow passage between said pilot inlet and pilot outlet whichis larger than said control passage to substantially equalize thepressure in said main pressure chamber with the pressure in said mainoutlet chamber.

7. An apparatus according to claim 6 wherein said control passagecomprises a passage formed in said means connecting said main pressureresponsive member to said main valve member.

8. An apparatus according to claim 6 including means defining a secondchamber at said other side of said main pressure responsive member, andmeans providing restricted communication between said second chamber andsaid main outlet chamber to inhibit rapid movement of said main pressureresponsive member and said main valve member.

9. An apparatus according to claim 8 wherein said main valve member hasmeans cooperating with said main valve seat to provide a sliding sealtherebetween during initial movement of said main valve member relativeto said seat.

10. An apparatus according to claim 6 wherein said main valve member hasmeans cooperating with said main valve seat to provide a sliding sealtherebetween during initial movement of said main valve member relativeto said seat.

11. In a pumping system including a delivery line, a flow control valvemeans at one end of the line for controlling fiow therefrom, pump meanscommunicating with the other end of the delivery line operable tointermittently deliver fluid under pressure to the line whereby thepressure in the line can vary from full pump delivery pressure when thepump is operating and the flow control valve means is closed to arelatively low pressure when the pump is stopped, means for detectingleakage in excess of a preselected leakage rate from the delivery linecomprising a casing having a main inlet chamber communicating with theoutlet of the pump and a main outlet chamber communicating with thedelivery line to pass fluid thereto, a main valve seat intermediate saidmain inlet and main outlet chambers, a main valve member controllingflow through said main valve seat and mounted for movement in thedirection of fluid flow through the valve to its open position, a mainpressure chamber, and a main pressure responsive member having one sideexposed to pressure in said main pressure chamber and the other sideexposed to pressure in said main outlet chamber, means connecting saidmain pressure responsive member to said main valve member for moving thelatter to a closed position in response to a preselected pressuredifferential between the main pressure chamber and the main outletchamber, control passage means communicating said main outlet chamberwith said main pressure chamber and dimensioned to pass fluid to themain pressure chamber at a rate in excess of said preselected leakagerate, a leak detector pilot valve including a pilot valve casing havinga pilot inlet communicating with said main pressure chamber and a pilotoutlet communicating with said main outlet chamber, pilot valve meanscontrolling flow from said pilot inlet to said pilot outlet, meansresponsive to the pressure in said main outlet chamber for positioningsaid pilot valve means in an initial position when the pressure in saidmain outlet passage is below a preselected intermediate pressure rangebetween said low pressure and said delivery pressure, said pressureresponsive means being operative to move said valve means to anintermediate position when the pressure in said main outlet passage isin said intermediate range and to an open position when the pressure inthe main outlet passage is above said intermediate range, said pilotvalve means being operative in said initial position to define aninitial flow passage between said pilot inlet and pilot outlet that issmaller than control passage means to pass fluid at a rate in excess ofsaid preselected leakage rate to said main outlet chamber to rapidlyfill the delivery line, said pilot valve means ineluding means operativewhen the pilot valve means is in said intermediate position to define anintermediate flow passage between said pilot inlet and pilot outletwhich is smaller than said initial flow passage to pass fluid at saidpreselected leakage rate to said main outlet chamber to increase thepressure in said main outlet chamber if the leakage from the deliveryline is less than said preselected leakage rate, said pilot valve meansincluding means operative in said open position to define a flow passagebetween said pilot inlet and pilot outlet which is larger than saidcontrol passage to substantially equalize the pressure in said mainpressure chamber with the pressure in said main outlet chamber.

1. An apparatus for detecting leakage in excess of a preselected leakagerate from a fluid delivery line through which fluid is intermittentlydelivered under pressure and wherein the pressure in the line can varyover a wide range between a low pressure and a relatively higherdelivery pressure, said apparatus comprising a casing having a maininlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat, and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, a main pressure responsive member having one sideexposed to pressure in the main pressure chamber and the other sideexposed to pressure in the main outlet chamber, means connecting saidmain pressure responsive member to said main valve member for movingsaid main valve member to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main pressurechamber with said main inlet chamber and dimensioned to pass fluid fromthe main inlet chamber to the main pressure chamber at a rate in excessof said preselected leakage rate, a leak detector pilot valve includinga pilot valve casing having a pilot inlet communicating with said mainpressure chamber and a pilot outlet communicating with said main outletchamber, pressure responsive pilot valve means for controlling flowbetween said pilot inlet and pilot outlet and operative to provide arestricted flow passage between said pilot inlet and said pilot outletto pass fluid at said preselected leakage rate when the pressure in saidmain outlet chamber reaches a preselected intermediate range betweensaid low pressure and said delivery pressure, said pressure responsivepilot valve means being operative when the pressure in said main outletchamber rises above said intermediate range to open and provide a flowpassage therethrough which is relatively unrestricted as compared tosaid control passage means whereby to substantially equalize thepressure in said main pressure chamber with the pressure in said mainoutlet chamber and allow said main valve member to open.
 2. In anapparatus for detecting leakage in excess of a preselected leakage ratefrom a fluid delivery line through which fluid is intermittentlydelivered under pressure and wherein the pressure in the line can varyover a wide range between a low pressure and a relatively higherdelivery pressure, said apparatus comprising, a casing having a maininlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, and a main pressure responsive member having oneside exposed to pressure in said main pressure chamber and the otherside exposed to pressure in said main outlet chamber, means connectingsaid main pressure responsive member to said main valve member formoving the latter to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main outletchamber with said main pressure chamber to apply fluid pressure to saidmain pressure responsive member for holding said main valve member inits closed position, pressure responsive control means operative whenthe main valve member is in its closed position and the pressure in themain outlet chamber is below a preselected intermediate pressure rangefor passing fluid at a preselected signal rate from the main inlet tothe main outlet to allow the pressure in said main outlet chamber torapidly build up to said preselected intermediate pressure range, saidpressure responsive control means including means operative when thepressure in said main outlet chamber reaches said preselectedintermediate pressure range to restrict flow from said main inlet tosaid main outlet to said preselected leakage rate, said pressureresponsive control means including means operative when the pressure inthe main outlet chamber rises above said intermediate pressure range topass fluid from said main pressure chamber to said main outlet chamberat a rate greater than the rate of flow of fluid through said controlpassage means into said main pressure chamber to thereby substantiallyequalize pressures on opposite sides of said pressure responsive memberand allow said main valve member to open.
 3. In an apparatus fordetecting leakage in excess of a preselected leakage rate from a fluiddelivery line through which fluid is intermittently delivered underpressure and wherein the pressure in the line can vary over a wide rangebetween a low pressure and a relatively higher delivery pressure, saidapparatus comprising, a casing having a main inlet chamber and a mainoutlet chamber adapted to pass fluid therethrough to the delivery lineand a main valve seat intermediate said main inlet and main outletchambers, a main valve member controlling flow through said main valveseat and mounted for movement in the direction of fluid flow through thevalve to its open position, a main pressure chamber, and a main pressureresponsive member having one side exposed to pressure in said mainpressure chamber and the other side exposed to pressure in said mainoutlet chamber, means connecting said main pressure responsive member tosaid main valve member for moving the latter to a closed position inresponse to a preselected pressure differential between the mainpressure chamber and the main outlet chamber, control passage meanscommunicating said main outlet chamber with said main pressure chamberand dimensioned to pass fluid to the main pressure chamber at a rate inexcess of a preselected signal rate, a leak detector pilot valveincluding a pilot valve casing having a pilot inlet communicating withsaid main pressure chamber and a pilot outlet communicating with saidmain outlet chamber, pressure operated pilot valve means controllingflow between said pilot inlet and said pilot outlet operative when thepressure in said main outlet chamber is below a preselected intermediatepressure range to pass fluid at said preselected signal rate from saidmain pressure chamber to said main outlet chamber, said pressureoperated pilot valve means being operative when the pressure in saidmain outlet chamber reaches said intermediate pressure range to restrictflow between the pilot inlet and the pilot outlet to said preselectedleakage rate, said pressure operated pilot valve means being operativewhen the pressure in said main outlet chamber rises above saidpreselected intermediate pressure range to open and pass fluid from themain pressure chamber at a rate greater than the rate of fluid flowthrough said control passage to thereby allow said main valve member toopen.
 4. An apparatus according to claim 3 including means defining asecond chamber at said other side of the pressure responsive member, ndmeans providing restricted communication between said second chamber andsaid main outlet chamber to inhibit rapid movement of said main pressureresponsive member and main valve member.
 5. An apparatus according toclaim 3 wherein said main valve member has means cooperating with saidmain valve seat to provide a sliding seal therebetween during initialmovement of the main valve member relative to the main valve seat.
 6. Inan apparatus for detecting leakage in excess of a preselected leakagerate from a fluid delivery line through which fluid is intermittentlydelivered under pressure and wherein the pressure in the line can varyoveR a wide range between a low pressure and a relatively higherdelivery pressure, said apparatus comprising, a casing having a maininlet chamber and a main outlet chamber adapted to pass fluidtherethrough to the delivery line and a main valve seat intermediatesaid main inlet and main outlet chambers, a main valve membercontrolling flow through said main valve seat and mounted for movementin the direction of fluid flow through the valve to its open position, amain pressure chamber, and a main pressure responsive member having oneside exposed to pressure in said main pressure chamber and the otherside exposed to pressure in said main outlet chamber, means connectingsaid main pressure responsive member to said main valve member formoving the latter to a closed position in response to a preselectedpressure differential between the main pressure chamber and the mainoutlet chamber, control passage means communicating said main outletchamber with said main pressure chamber and dimensioned to pass fluid tothe main pressure chamber at a rate in excess of said preselectedleakage rate, a leak detector pilot valve including a pilot valve casinghaving a pilot inlet communicating with said main pressure chamber and apilot outlet communicating with said main outlet chamber, pilot valvemeans controlling flow from said pilot inlet to said pilot outlet, meansresponsive to the pressure in said main outlet chamber for positioningsaid pilot valve means in an initial position when the pressure in saidmain outlet passage is below a preselected intermediate pressure rangebetween said low pressure and said delivery pressure, said pressureresponsive means being operative to move said valve means to anintermediate position when the pressure in said main outlet passage isin said intermediate range and to an open position when the pressure inthe main outlet passage is above said intermediate range, said pilotvalve means being operative in said initial position to define aninitial flow passage between said pilot inlet and pilot outlet that issmaller than control passage means to pass fluid at a rate in excess ofsaid preselected leakage rate to said main outlet chamber to rapidlyfill the delivery line, said pilot valve means including means operativewhen the pilot valve means is in said intermediate position to define anintermediate flow passage between said pilot inlet and pilot outletwhich is smaller than said initial flow passage to pass fluid at saidpreselected leakage rate to said main outlet chamber to increase thepressure in said main outlet chamber if the leakage from the deliveryline is less than said preselected leakage rate, said pilot valve meansincluding means operative in said open position to define a flow passagebetween said pilot inlet and pilot outlet which is larger than saidcontrol passage to substantially equalize the pressure in said mainpressure chamber with the pressure in said main outlet chamber.
 7. Anapparatus according to claim 6 wherein said control passage comprises apassage formed in said means connecting said main pressure responsivemember to said main valve member.
 8. An apparatus according to claim 6including means defining a second chamber at said other side of saidmain pressure responsive member, and means providing restrictedcommunication between said second chamber and said main outlet chamberto inhibit rapid movement of said main pressure responsive member andsaid main valve member.
 9. An apparatus according to claim 8 whereinsaid main valve member has means cooperating with said main valve seatto provide a sliding seal therebetween during initial movement of saidmain valve member relative to said seat.
 10. An apparatus according toclaim 6 wherein said main valve member has means cooperating with saidmain valve seat to provide a sliding seal therebetween during initialmovement of said main valve member relative to said seat.
 11. In apumping system including a delivery line, a flow control valve means atoNe end of the line for controlling flow therefrom, pump meanscommunicating with the other end of the delivery line operable tointermittently deliver fluid under pressure to the line whereby thepressure in the line can vary from full pump delivery pressure when thepump is operating and the flow control valve means is closed to arelatively low pressure when the pump is stopped, means for detectingleakage in excess of a preselected leakage rate from the delivery linecomprising a casing having a main inlet chamber communicating with theoutlet of the pump and a main outlet chamber communicating with thedelivery line to pass fluid thereto, a main valve seat intermediate saidmain inlet and main outlet chambers, a main valve member controllingflow through said main valve seat and mounted for movement in thedirection of fluid flow through the valve to its open position, a mainpressure chamber, and a main pressure responsive member having one sideexposed to pressure in said main pressure chamber and the other sideexposed to pressure in said main outlet chamber, means connecting saidmain pressure responsive member to said main valve member for moving thelatter to a closed position in response to a preselected pressuredifferential between the main pressure chamber and the main outletchamber, control passage means communicating said main outlet chamberwith said main pressure chamber and dimensioned to pass fluid to themain pressure chamber at a rate in excess of said preselected leakagerate, a leak detector pilot valve including a pilot valve casing havinga pilot inlet communicating with said main pressure chamber and a pilotoutlet communicating with said main outlet chamber, pilot valve meanscontrolling flow from said pilot inlet to said pilot outlet, meansresponsive to the pressure in said main outlet chamber for positioningsaid pilot valve means in an initial position when the pressure in saidmain outlet passage is below a preselected intermediate pressure rangebetween said low pressure and said delivery pressure, said pressureresponsive means being operative to move said valve means to anintermediate position when the pressure in said main outlet passage isin said intermediate range and to an open position when the pressure inthe main outlet passage is above said intermediate range, said pilotvalve means being operative in said initial position to define aninitial flow passage between said pilot inlet and pilot outlet that issmaller than control passage means to pass fluid at a rate in excess ofsaid preselected leakage rate to said main outlet chamber to rapidlyfill the delivery line, said pilot valve means including means operativewhen the pilot valve means is in said intermediate position to define anintermediate flow passage between said pilot inlet and pilot outletwhich is smaller than said initial flow passage to pass fluid at saidpreselected leakage rate to said main outlet chamber to increase thepressure in said main outlet chamber if the leakage from the deliveryline is less than said preselected leakage rate, said pilot valve meansincluding means operative in said open position to define a flow passagebetween said pilot inlet and pilot outlet which is larger than saidcontrol passage to substantially equalize the pressure in said mainpressure chamber with the pressure in said main outlet chamber.